Dan,
I think it is wonderful of you to take up this quest for donations in Heather's memory. Keep in mind though, that lots of people either don't use credit cards or don't feel comfortable using them online. I think some people will be mailing their donations, so it will take awhile to get a good accounting. Also, some people are on fixed or limited incomes and really can't afford a
donation. Although I don't think your figure of 25% being able to do so is unrealistic. I guess time will tell.
Thanks,
Rosie